Fluorescent street lighting system



P 9, 1952 A. M.- MILES 2,610,310

FLUORESCENT STREET LIGHTING SYSTEM Filed June 2, 1948 2 SHEETSSHEET l m5 0 0 2: 105 INVENTOR. O 102 A7. 44. 44/455 INVENTOR.

A M. M/LE5' 2 SHEETS-SHEET 2 A M MILES FLUORESCENT STREET LIGHTING SYSTEM Sept. 9, 1952 Filed June 2, 1948 Patented Sept. 9, 1952 gt i gpsTATEs PATENT OFFICE Alfred M. Miles, Spartanburg, S. C. Application J une Z, 1943, Serial N0. 30,670

1 i This invention relates to an improved fluorescent or gaseous discharge lighting system particularly suited for outdoor use and especially for street lighting. One of the important features of the invention is the provision of a high power factor system without the' usual' expensive auxiliary equipment. g

This application is a continuation-in-part of my application Serial Number 592,216, filed May 5, 1945.

As is well known, the power factor of fluorescent or gaseous discharge lamp circuits is very low due to the reactors or chokes which must ordinarily be used to initiate the operation of such lamps. It has already been suggested heretofore that the power factor of fluorescent light system circuits can be improved by operating two such lamps in parallel from a common source of power; one lamp beingoperated in series with a reactor to give a lagging current while the other is operated in series with a condenser to give a leading current, the combined effect producing substantially unity power factor. It has also been suggested heretofore that the power factor of a circuit including fluorescent lamps can be improved by operating the lamps in series. This latter suggestion has been made in connection with lamps which are operated from the usual commercial constant volt age source of 1'10 to 120 volts. In both of these systems which usually use a low operating voltage, it is necessary to provide special equipment for the initiation of the gaseous discharge in thelamps. A special problem would develop if itwas'attempted to operate lamps in accordance with the-previously mentioned systems in cold weather due to the fact that a minimum temperature must be reached in the lamp before the gas will ioni ze to initiate the operation of the tube because the voltage available is not very high.

In the conventional street lighting circuits the lamps on the different lamp posts are usually'conected in series, suitable regulating apparatus beingprovided to maintain'the proper amperage at constant voltage and automatic devices being provided to bridge the circuit around any defective lamp in order that the remaining lamps in the circuit can continue to operate. The advantage of the series circuit is lower initial cost and the operating characteristics can be made more uniform. Heretofore arc lamps and incandescent lamps have been used in such series street lighting circuits but as far as is known the operation of fluorescent or gaseous discharge lamps under the conditions encoun- 5 Claims. (Cl. 315-) tered in outdoor street lighting has been considered to be impractical except possibly under the most ideal conditions. The primary difficulty in providing an outdoor fluorescent lighting system which could be used under variable outdoor temperature conditions is the initiation of the gaseous discharge and maintaining the lamp at the proper operating temperature for maximum efiiciency.

Accordingly, one of the primary objects of the present invention is to provide a lighting system which can be used in outdoor street lighting. I Another primary objectis to provide a lighting system employing the dual voltage gaseous discharge lamps without substantially lowering the power factor.

Another object is to provide a series lighting system for fluorescent lamps in which means is provided for maintaining the operating current within the lamps in series at a substantially constant value in order not to damage the lamps and to permit the continued operation of the good lamps in the series in the event one of the lamps becomes defective or in the event the starter for one of the lamps becomes defective so that that lamp does not operate.

A still further object is to provide a lighting circuit arrangement in which two or more hot cathode gas discharge lamps are provided with appropriate starting devices for the individual lamps in such a manner that in the event of failure of one of the lamps its associated starter will close to serve as a circuit closing device to close the series circuit to permit the operation of the other tube or tubes in the series circuit. A. more specific object is to provide a lighting systememploying two or more hot cathode fluorescent lamps in a series circuit with a plurality of starters connected in parallel for each lamp, one of the starters being of the thermal type so as to operate the lamps in cold weather, and the other being of the gaseous type and having a higher voltage operating characteristic whereby the starter with the higher voltage characteristic can serve to protect its associated lower starter in the event of failure of the associated fluorescent lamp and at the same time serve as a circuit closing device for the other lamp or lamps.

Other and further objects of the invention will. appear from the following description taken in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic view of the street lighting circuit showing the manner in which a 3 plurality of the devices in accordance with the present invention might be used;

Figure 2 is a diagrammatic view of a component of the lighting system embodying the principles of the invention;

Figure 3 is a side elevation of a lighting fixture in accordance with the present invention;

Figure 4 is a bottom plan view of the base of the fixture; a

Figure 5 is an end view of Figure 3 Figure 6 is a side elevation showing the construction of the louvered shade of the fixture} Figure '7 is an enlarged cross section taken along the line 1-! of Figure 6;

Figure 8 is an enlarged cross sectional eleva tion of the thermostatic type starter and exemplifying the principles of the present invention;

Figure 9 is a cross sectional elevational view of gaseous glow type starter exemplifying the principles of the present invention;

Figures 10 and 11 are modified forms of the circuit diagram exemplifying the invention.

Referring specificallyto Figure 1' of the drawings,.the-present invention is illustratedas being adapted for series street lighting systems wherein a series circuit, 'forexample, may supply all of the lamps in one block. The lamps on the individual lamp posts can be energized from the series circuit through a single constant current transformer or other suitable regulating equipment indicated at I. Alternately, individualtransformers 2, having their primaries connected in the series circuit for the block, could be utilized at each lamp post to supply the lamps on each lamp post in series. The only purpose of the transformers is to adapt the ampere demand of the lamp to the ampere characteristics of the line and to isolate the fixture from the distribution voltage, If the lamps on each individual lamp post are energized by a separate transformer, theregulating apparatus I- would be of the type to provide a constantcurrent to the primary circuit regardlessof the total load taken by the diiferent transformers. Also, the individual transformers 2 would be so designed as to provide a constant current output regardless of the load on the respective secondaries, that is, the transformers would be designed for high power factor and would have a low leakage magnetic. circuit. This is essential for the continued operation of some of the lamps in series in accordance with the present invention in which itwill be understood the regulation is due to thelconstant current supply when one or more of the other lamps may be defective. It will also be apparent to those skilled in the art that if the 'primariesof the individual transformers 2' were connected to the usual commercial source of power, the transformers would be so designed. as to have constant current characteristics for the same purpose. In the latter event the lamps at the different lamp posts would be connected in series across the secondary 3 of the transformer. as indicated in Figure 2. It will be readily-understood that if desired the different lamps on two or more lamp posts might be connected in series in accordance with the present invention in an arrangement such as that shown in Figure 11.

Referring specifically to Figure 2,- the reference characters [0 and represent two fluorescent lamps of the dual voltage hot cathode type having filaments at the opposite ends thereof. By dual voltage type is meant that the 4 lamps are of the type which are started by a peak voltage of short duration after the hot cathodes have initiated the ionization of the gases inside the lamp and are thereafter operated at a lower voltage. In the operation of such lamps the filaments or hot cathodes are connected in a series circuit across a suitable source of alternating current indicated herein by the secondary 3 of the 'transfornier, 2. As will be understood from this description, a constant current supply is utilized, instead of the usual constant voltage supply, and for this reason no inductance is required to start the lamps in the series circuit. Because of the inherent nature of the constant current supply circuit,

. any tendency to open-circuit the load side immediately results in an increase in voltage so 1 that upon open-circuit a peak voltage is produced. It is for this reason that an initial peak voltage is produced to start the operation of the lamps ,when the power is appliedto the primary of the transformer. 5

Suitable heater type starters 4 and 5 are connected in series with the filaments 30'of theffiucrescent lamps, the starter 4 being associated with the lamp l0 and the starter 5 beingassociated with the lamp .201 Gaseous glow 1 discharge type starters II and I2 are connectedin parallel respectively with heater type starters 4 and 5. As will bedescribed later, these gaseous glow discharge type starters have a high breakdown voltage characteristic so that. normally the lamps will bestar'ted in the conventional manner by the heater type starters 4 and 5 but in the event of failure of one of the lamps the associated glow discharge starter will break down.

and serve to dissipate the are between the contacts of the heater type starter when it at-.

tempts to start the defective tube and at the same time will. serveas a temporary circuit closing. device so that the other tube may continue to operate r In general, assuming that the line circuit is closed, the secondary of the transformer will become-energized passing current through the four serially connected filaments 30 through the closed contacts of the thermostatic starter. .If the starter 4, for example, breaks first, the arc will bestruck through the tube ID. If when the starter 5 breaks, an arc is simultaneously struck in the-tube 213, the secondary circuit remains,

closed and both tubes remain lit. If, however, in the absence of the glow starters the first opening ofstarter 5 fails to strike an arc, the circuit is broken and the arc in the tube I 0 extinguished. The thermostatic starters make repeated tries and if the tube 20 is bad the tube [0 remains lighted when the starter 5 finally assumesits locked closed position.

The two principal drawbacks of such an arrangement are: (1) 'Due to the high voltage passing through the -secondary circuit when one tube fails: to operate, there will be excessivearcing between the contacts of the thermostatic starters, resulting in rapid destruction of the starters and possibly other parts of the fixture. (2i Intermittent action of the good tubes due to repeated opening and closing of the thermostatic'st'arter associated with the bad tube, un-

til said starter finally locks closed.

The presence of the gaseous glow starters gaps of the thermostatic connected across the starters remove both of these objections. Should one fail to light promptly when the points of its associated thermostatic starter sep:

arate the first timathe other tube or tubes on the same ballast, are'not deprived of operating power, for the gaseous glow starter automatically ionizes and maintains the current constant to the'j other tube ortubes until operation is properly established in the first tube, or until the thermostatic starter of the first tube finally locks closed. Thus, .the functionof the gaseous starter in this case, although it is a conventional type starter, is not as a starter, but the action is that of a temporary circuit closing device."

When one tube does not promptly strike an arc,'or .is bad, so that the thermostatic starter makes several tries before assuming closed locked position, the gaseous starter prevents arcing by ionizing and carrying the current of the series circuit.

.The details of the heater starting devices 4 and 5 are shown in Figure 8 while the details of the gaseous glow discharge type starters II and H are shown in Figure 9.

The starters are all provided with a so-called no-blink feature in that they are adapted to close their contacts to close the series circuit between their terminals after a'few unsuccessful attempts to start their associated lamp. Referring specifically to Figure 8, the heater type starter comprises a suitable casing l3 which is provided with a suitable insulating base plate l4 having two projecting terminals l6 and I1 which are adapted to engage contacts in the conventional starter socket, the terminals of which, of course, would be connected in the lamp circuit in the well known manner. A suitable insulating supporting plate It! is mounted on the base plate M on which the other elements of the starter can be mounted. A suitable heater resistor I9 is connected between the terminals 16 and i1. Associated in close proximity thereto is a bimetallic thermal member [5. The lower end of the bimetallic member I5 is connected to the terminal l1 and the upper end of the member I5 is provided with a suitable contact 2|. A plurality of contacts 22 and 23 are mounted on the insulating plate |8 and are connected through a separate heater resistor 24 to terminal i6. A secondbimetallic thermal member 26 mounted on the insulating plate I8, is associated in thermal relation. to the heater 24 and is adapted to operate under the influence of heat from the, heater .24 to short-circuit'terminals l6 and -H. To this end, an armature 21 is pivotally mounted on the base plate l8 and is electrically connected through the conductor 28 to terminal H. The upper end of the bimetallic thermal member 26 is provided with a latch 29 which is adapted to engage the outer end of the armature 21, the latter being spring biased in an upward direction by means of appropriate tension spring 3|. A suitable contact 32 is electrically connected by suitable conductor 33 to terminal l6. Contact 34 on the armature 21 is adaptedto cooperate with the contact 32 to short-circuit the terminals I5 and I1 when the latch 29 is disengaged from the outer end of the armature 21. A suitable condenser 35 is preferably connected across the terminals I6 and I! to reduce the radio interference. A suitable reset button 31 extending through an aperture in the top of the casing I3 is provided for the purpose of manually returning the armature 21 to the initial position.

The starter and safety device shown in Figure 8 operates as follows: Assuming that the terminals l6 and I! are connected in a circuit in series with the filaments of a fluorescent lamp in the position shown in Figure 2, when no power is applied to the circuit the contacts 22 and 2| are closed. When power is applied as byenergization of the primary of the transformer 2, the circuit will be closed through the filaments,

of both of the lamps I0, 20. The heater resistor 19 is of very low capacity and develops only enough heat to cause the bimetallic member IE to operate. The thermal characteristics of the member I5 are such that contacts 22 and 2| remain'closed long enough to preheat the filaments 30 so, that the lamps ID, 20 are conditioned for glow discharge operation. When thecontacts 22 and 2| open, the necessary high voltage peak for starting the associated lamp becomes available because of the constant current characteristics previously mentioned. As willbe seen from Figure 8, the heater |9 remains in series with the circuit which energizes the glow discharge and supplies enough heat to the member l5 to cause the contact 2| to remain in an intermediate position between electrodes 22 and 23. In the event the lamp ID is defective or fails to continue its glow discharge operation after the initial starting cycle the higher current through the filaments will cause the heater 9 to raise the temperature of the member l5 so that 'contacts 23 and 2| will be closed. When contacts 23 and 2| are closed, the heater 24 is placed in parallel with the heater l9, causing the latter to cool and the bimetallic member l5 to open contacts 2| and 23. This cycle of operation con tinues until the cyclic operations cause the bimetallic member 26 to become sufficiently heated so that its upper end bends to the left so that latch 29 is disengaged from the armature 27, thus permitting the spring 3| to move the armature 21 to close the contacts 32 and 34, thereby short-circuiting the terminals l6 and I1 and preventing further automatic starting cycles until the reset push button 31 is manually operated to reengage the latch 29 on the outer end of the armature 21.

In Figure 9 is shown the details of the gaseous glow discharge type fluorescent lamp starters which are designated by the numerals H and I2 in Figure 2. As in the heater type shown in Figure 8, the unit comprises an outer casing 4| provided with cars 42 which are adapted to engage an insulating base 43. The insulating base 43 has the conventional terminals 44 and by means of which the starting unit is mounted in the conventional starter socket and by means of which the starter is connected into the lamp circuit. Also, as in the heater type starter a suitable insulating supporting plate 41 is mounted on the base plate 42 and is adapted to support the different elements of the starter unit.

The usual condenser 48, for the purpose of reducing radio interference, is connected between the terminals 44 and 46. In general, the starting unit of Figure 9 is quite similar to the starting unit shown in Figure 8 except that in the former a'glow tube type starting switch 49 is used instead of the heater type starter. The glow type switch is preferably of the type shown in U. S. Patent to Dench 2,200,443, which comprises a glass envelope 5| having a gaseous environment therein such as neon, argon or a similar ionizable medium. A suitable bimetallic member 52 has its upper end provided with a contact 53, the lower end of the member being fixed in the press of the envelope. A second 7 contact '54 is adaptedto' cooperate with the con tact53in circuit closing relation and is 'sup-- ported "by a" suitable terminal mounted in the press of th'e' envelope A suitable heater resistor 56 is connected in series with the glow type switch 49 between the terminals 44 and 46. The heater 56 is'in'thermal relation to a suitabl'eibi metallic member 51, the lower'endof-which is fixed to the insulating supporting 'plate41- and the upper end is provided with a'suitabledatc'h. 58. The latch 58-is 'adaptedto en'gage theouter end of anarmature 59, 'one'end of which is piv oted at 6| to'ithe insulating supporting plate 41'. The armature 59 is provided with a suitable contact 62'which is operably associated withycon; tact 63 fixed to the supporting plate 4I. Aswill appear from the drawing, contact vI33 is connected to'ithe terminal 46, and the armature 59 and :its contact 62 are'electrically connected to the terminal'44. A suitable tension spring 64 isadapted to urge theouter end orthe armature 59 in the'upward direction against the latch 58 andto close contacts 62 and 63 when the latch 58. is disengaged from the outer end of the armature. A suitable reset button 56 extends upwardly through an aperture in top of the'casing M and is provided with'a suitable actuating stem 51 which is adapted to engagethe armature 59 to the left of the pivotal connection 6| so that'the lock-out mechanism of the starting unit can be reset; The operation" ofthi's glow type starteris similar tothat of the heater type starter except that the former has a higher voltage and longer pre-heat characteristic for a purpose which will be'app'arent from description hereinafter. Assuming that no power. is applied to the circuit in which the heater unit is connected, the contacts 53' and 54 will be open. If the voltage applied across the terminals 44 and46 is sufficient to initiate the glow discharge inthe switch- 49 the bimetallic-member 52 will become heatedand thus cause the contacts 53, 54 to close. This will close the circuit between the terminals 44 and 46 through the heater: 56 and assuming the starting unit is connected in thepositionfshown at II or I2 in Figure 2, the circuit through the cathodes 30 would :be closed to cause. them to pre-heat. Assoon as the'contacts 53 and 54 areclosed, the .glow discharge in the switch 49 will stop. This will allow'the'bimetallic-member 52 to cool, thus again'opening the contacts 53 and 54. However, the characteristics of the thermal switch 49 are so related to thestarting characteristics of'the fluorescent lamps: that under normal conditions the cathodes'35fiwil1have been heated to the "point that the glowdischarge between cathodes 30 will' be initiated when the contacts 53 and 54 open. So long as the glow discharge in the lamps IB' and remains'active, the voltage drop across the devices I I and I2 (terminals 44 and 46) willinot be sufiicient to initiate the low discharge in the switch 49 and therefore the glow starter-remains inactive. However, irrtheevent the lamp Abecomes defective and does not operate, theglow discharge starting unit will attemptto reinitiate the glow discharge in the fluorescent lamp. In the event that the fluorescent lamp is defective ordoes not continue to operate after'the first starting cycle, the glow' discharge starting unit will repeat-its starting cycle until-theintermittent operation of the-resistor 56 raises the tem= perature of the bimetallic member 5'Ito the point where the latch 58 disengages the outer end of the armature 59, thus closing the con'- tacts '62 and-63 and short-circuiting "the ter minals-144Iand 46. It will be readily' seen that when'this :happens' the series circuit will be closed: through'ithelamp cathodes so that'i'the o'ther lamp orlampdn series can continue to operate. i

FNQW referring ag'ainto Figure=2, by .using two starterJunits'i-Of: different voltage characteristics in. parallel in the series' fluorescent-lamp circuit, it will'be'understoodthat thestarter havin'g th'e lower voltage and lower pre-heat characteristic will normally start the associated lamp, it being understood that 'heater type starters are preferred forcold weather conditions' In the form of the invention illustrated herein the-reference numerals 4 and 5 represent startershaving the lower voltage and pre-heat characteristics while the reference numerals I I and I2 represent starters having a higher'voltage 1' and a'lon'ger-p'reheatfcharacteristic', the starters land '5 being of the heater type and the starters'II and I2 being of the gaseous glow type. However, should a glow type starter having a suifficiently long'preheat "and other characteristicsto operate lamps exposed'to low temperatures become available, it could be substituted for the present starters 4 and II as used in parallel. When the heater type starters 4; 5 and the glow type starters II; I 2 are used in parallel, the glow type starter serves to prevent the-flash-over of the points of the'heater starter while the heater starter is going through the starting cycles anduntil it closes its contacts after several unsuccessful attempts to start the tube. At the same time; the glow type starter is serving as a temporary circuit closing device for the other fluorescent lamp or lamps in the series circuit it also serves asa protection to the contacts of its associated heater starter, and as a starter under abnormal conditions. Byway'of example, upon the appli-' cation of power to the series lamp circuit shown in Figure2 the circuit through the filaments of lamps I0 and 29 would normally be closed through'the thermostatic starters 4 and 5. If, for instance, the lamp I6 is defective and fails to, continue to burn'after the starter contacts areopen, the starter will again closeits contacts and make several attempts to'start the lamp'. In the meantime the glow type starter II serves to dissipate the energy in the are between the points of the'thermostatic starter 4 and thereby prevent excessive burning thereof. At the same time, due ,to the fact that the lamp II] is'not in operation, the voltage drop would be suflicient to operate the glow type starter'l'I so that it closes its contacts to complete the circuit through the lamp 26; In this way the function of the glow type starter is as a temporary circuit closing device. Assuming that the glow type starter II has closed its contacts, the lamp 20 will be started by the operation of the glow type starter. Normally this lamp would be started by the operation of-its associated heater type starter 5. If the lamp I0 eventually fails to start after several attempts on the part of its heater type starter 4, the latter will close its contacts, thus short-circuiting the glow type starter II so that it is no longer in operation and the circuit will be permanently closed through the lamp 2U. This,'of course, is assuming that the filaments of the lamp} 0- have not burned out. As is well known, the fluorescent operation of the lamp usually becomes defective before the filaments thereof become defective. It will be understood from the foregoing description that even though one of 9. the iiuorescent lamps in the series becomes defective and the special starting. device shorts out the defective lamp, the remaining lamp or lamps in series can-be operated because in accordance with the present invention the power. source has a constant current characteristic so that regardless of the number of lamps operating in the series circuit the voltage drop. across the individual lamps will remain substantially constant.

Figures 10 and 11 show modified forms of the circuit arrangement shown in Figure 2 using the type of starters illustrated in detail in Figures 8 and, 9. The only difference between the circuit of Figures 10 and 11 is that Figure 11 shows three lamps in series across a single source of power. It willbe'readily understood that the number of lampsin series could be increased in any desired amount by merely applying the necessary higher voltage.

Referring specifically to Figure 10, a plurality of fluorescent lamps I8 and II areconnected in series across the secondary of transformer I3 which might correspond to the transformer 2 of Figure 2. An appropriate heater type starter Hi and; a glowtype starter TI are connected in parallel in a series circuit including the filaments of the tube ID and tube I I, the series circuit being completed through heater starter 16 and glow type starter is which are connected in parallel in a manner similar to the corresponding elements described in connection with Figure 2. The operation of the different starters and the fluorescent lamps is the same as in the circuit arrangement of Figure 2. In addition to the elements shown in Figure 2, additional glow type starters I9 and BI are connected in series across the two sides of the input to the series circuit and an intermediate point between these starters isconnected by the conductor 82 to a point 83 which is electrically common to terminals of the filaments of the tubes I and H in such a manner that the glowtype starters I9 and 8| are each connected in parallel in the series circuit through the filaments of the individual lamps and their respective starters. The glow type starters I9 and 8I are identical and are similar to the glow type starters Ti and I8 except that the starters I9. and BI have a higher voltage rating so that they are inoperative so long as the circuit exists through the lamps or associated starters across which it is connected, whether this circuit be completed through the'lamp filaments or through gaseous discharge conduction. The purpose of the glow type starters IB'and BI is to shunt out of the'circuit any lamp which, with its associated starters, might under certain abnormal condit'ions' present an open circuit. This permits the remaining lamps of the circuit to function normally and also prevents the formation of destructive arcs which might otherwise occur if the series circuit is accidentally opened when one of the lamps becomes defective or is broken. In the event one of the tubes should fail, the associated glow type starter I9 or M, whichever is the case, would become conducting and close the circuit so that the remaining lamp or lamps would operate in a normal manner. In such event it will be understood that the high voltage glow type starter would go through the normal starting cycles of attempting to start a defective lamp and when the lamp failed to start the lock-in feature would operate so that a device similar to the latch 58 of the device shown in Figure 9 would disengage an appropriate arma-.

10 ture to close the circuit through the respective glow type starter.

It will be noted that the circuit diagram of Figure'll is'merely an extension of that shown in Figure 10 and that the part of the circuit including the lamps 84 and 86 is identical to the arrangement of Figure'lO, the lamp 81 and its associated starter merely being an addition to the type of circuit shown in Figure 10, appropriate glow type starters 88, 89 and GI being connected in parallel with the filaments and the respective starters for the respective lamps. As in the previous circuit arrangements, the lamp 84 is provided with a heater type starter 92 and a glow type starter 93 connected in parallel arrangement in series with the filaments of the lamp. Likewise a heater type starter and a glow type starter 96 are connected in parallel arrangement in series with the filaments of lamp 86 and heater type starter 91 and'glow type starter 98 are connected in parallel arrangement in series with the filament of the lamp 81. As in the previous modifications, the pre-heat characteristics of the heater type starters 92, 94 and 9'1 are longer than those of the glow type starters 93, 96 and 98. Likewisethe voltage rating of the glow type starters 93, 96 and 98 are higher than the associated heater starters 92, 94 and 91, respectively.

The Figures 3 to '7 inclusive show a practical embodiment of a lighting fixture incorporating the operating system of the present invention. It comprises a hollow base I00 in which the power transformer such as transformer 2, may be housed, having a socket IOI on the underside thereof to receive a lamp post, not shown. There are three sockets at each end of the underside, accessibly placed, two of these being sockets I02 and I03 for suitable testing instruments. The socket I02, being connected in series with one of the power lines, is adapted to normally receive a circuit-closing plug which can be removed to permit the insertion of a plug of a testing device. The socket I03 is connected in parallel with the power source. ture to be supplied by an auxiliary power supply without otherwise disturbing the power supply line. Thus any fixture may be tested in the daytime, for example, Without placing the nor mal high operating voltage on the supply line. The other sockets I04 and I05 are adapted to receive the heater starters 4 and 5 respectively and the sockets III and H2 are adapted to receive the glow type starters II and I2 respectively. It will be understood that as far as the present invention is concerned, the exact arrangement of the location of the conventional.

sockets for holding the starters is immaterial so long as they are conveniently accessible for ready replacement and are properly protected from the weather.

The laterally projecting sockets Ill and H8 are adapted to receive the lower end of the vertically positioned fluorescent lamp I0 and 20, respectively. A suitable supporting tube II9 is secured to the top side of the base I00 between the tubes and extends vertically. The supporting tube II9 contains insulated wires which lead to the upper filaments of the lamps I0 and 20 through terminals I2I, I22 of a plug I23 fitted into an elongated cap I24.

The cap I24 is provided with openings at its underside near its opposite ends for receiving sockets I21 and I28 into which the terminals of the upper ends of the respective lamps I0 and 20 This permits the fix-' 11 are engaged. The elongated cap I24 may be of any suitable insulating material and is preferably provided with suitable conductors I20 and I25 embedded therein for connecting the ter-' minals I 2I and I22 to one of each of the sockets I21, I28, respectively; The other terminal of the sockets I27, I28 would .beso connected by suitable conductor I26 to form the series circuit shown in Figure 2, it being understood that the lower ends of the insulated wires in the post I I9 would be connected to the appropriatestarts,

ers to complete the circuit shown in Figure 2..

The upper .end of the supporting tube II9, is provided with a resilient collar I29 near its upper end on which the cap I24 rests. It will be readily seen that the cap I24 may beremoved,

by moving itupwardly away from the supporting tube H9 and the lamps I and 20. The location of the plug I23 and sockets I21 and I28 on the underside of the cap I24 prevents ingress of water to the interior of the cap. 7

In order to maintain satisfactory efficient op-' eration of the fluorescent lamps, in low temperatures, it is desirable to reduce the radiation of heat from the lamps. For accomplishing this result and for directionally controlled illumina-,

tion the individual lamps may be provided with, surrounding shades. These may be in the form of'louvered metal cylinders I3I as shown in Fig-- ures 6 and 7 or glass cylinders I32, preferably with refraction ridges as shown in Figures 3 and 5. The type of cylindrical shade shown in Fig-,

ures 3 and is continuous and spaced from the wall of the lamps providing air insulation which conserves the heat of the tube and prevents excessive cooling in cold climates.

The louvered shade shown in Figures 6 and 7 consists of a plurality of spaced annular bailles spotwelded or otherwise secured to rods I33 In servicing .a lighting fixture the cap, I24 is firstv removed, the defective lamps substituted by new ones, and the cap replaced. The weight, of the cap keeps the resilient contacts of all'the electrical sockets pressed against the corresponding terminals.

Although the invention has been described inf considerable detail it will be apparent to those skilled in. the art that many variations are pos-' sible without departing from the inventive con-. cept. It is, therefore, desired that the invention not be limited except insofar as it is made necessary by .the prior art claims. 7 7 What is claimed is:

1. A fluorescent lighting system comprising a source of alternating current, a, plurality of hot cathode gaseous discharge tubes each having a pair of cathode filaments, saidcathode filaments-'- being intercoupled in a series circuit across said source of alternating current, current peaking,

means in said series circuit, thermostatic make and break starters individual to said tubes of the type having normally closed bimetallic con-'- tact means heated on conduction of current therethrough for periodically open-circuiting the contacts for preselected intervals, said contact means being intercoupled across the fila-: ments of the tube associated therewith, and gaseous starters of the type'having normally 3 open bimetallic contact means enclosed in an ionizable medium which is ionized on occurrence 1 of preselected break-down voltage across the contacts thereof to close said open contact. means for a preselected interval, the normally open.

contact means of said gaseous starters being and by the appended:

connected across the contacts. of ,each of said thermostatic starters, said gaseous starters being ionized to close the contact means thereof onopening of said thermostatic starter contact means intercoupled therewith and failure of their associated gaseous discharge tube to conduct.

1 2. A fluorescent lighting system comprising a source of alternating current, a plurality of hot cathode gaseous discharge tubes each having a pairof cathode filaments, the cathodefilaments being intercoupled in a series circuit across said source of alternating current, current peaking means in said series circuit, thermostatic make and break starters individual to said tubes of the type having normally closed bimetallic contact means heated on conduction of current therethrough for periodically open-circuiting the contacts for a preselected interval, said normally closed contacts being intercoupled across the filaments of the tube associated therewith, and gaseous starter switch means coupled across the contacts of said make and break starters of the type having normally open bimetallic contact means enclosed in an ionizable medium which is ionized on occurrence of preselected break-down voltage across the contacts thereof to close said open contact means for a preselected interval, said switch means having a relatively higher voltage rating than said thermostatic starters to permit the make and break i the thermostatic starter intercoupled therewith and failure of their associated cathode tube to conduct, whereby ionization of said switch means effects closing of the contact means thereof to shunt out its associated thermostatic starter and cathode tube during open-circuiting of its associated thermostatic starter and non-conduction of its associated cathode tube,

3. A-fluorescent lighting system comprising a source of alternating current, a transformer" having a constant current secondary circuit, a plurality of, dual voltage hot cathode gaseous discharge lamps each having a pair of cathode filaments intercoupled in series in said secondary circuit, thermostatic make and break starters of the type having normally closed bimetallic means heated on conduction of current therethrough for periodically open-circuiting the contacts for a preselected interval, said normally 4 closed contacts being intercoupled between the terminal of each of said cathode filaments of each of said lamps to be alternately open-cir-j cuited and closed on energizing the series circuit and to initiate a conductive glow discharge between the cathodes on open-circuiting of said contacts, and gaseous discharge starter switch means having normally open bimetallic contact means enclosed in an ionizable medium which is ionized on occurrence of preselected break-down voltage to close said open contact means for a preselected interval, said normally open contact means'being intercoupled in parallel with each of said'thermost'atic make and break starters, and said gaseous switch means being ionized to close the contacts thereof on interruption of the cont-acts of their associat-- 4. A fluorescent lighting'system comprising a source of alternating current, a transformer coupled thereacro-ss having a constant current secondary circuit, a plurality of dual voltage hot cathode gaseous discharge lamps having pairs of cathode filaments intercoupled in series in said secondary circuit, a thermostatic make and break starter individual to each of said lamps having normally closed bimetallic means intercoupled across the filament of its associated lamp heated on conduction of current therethrough for periodically open-circuiting the contacts for a preselected interval, and a gaseous discharge starter of the type having normally open bimetallic means enclosed in an ionizable medium which is ionized on occurrence of a preselected breakdown voltage across the contacts thereof to close said open contact means for a preselected interval, said normally open contact means being intercoupled in parallel with each of said thermostatic starters, said gaseous starters having a relatively higher voltage rating than its associated thermostatic starter for preventing ionization of the medium of said gaseous starters on open-circuitin-g of ALFRED M. MILES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,503 Campbell June 27, 1944 1,960,408 Brach May 29, 1934 2,117,754 Bell May 17, 1938 2,286,790 Dench June 16, 1942 2,292,064 Dorgelo Aug. 4, 1942 2,374,315 Whiteside Apr. 24, 1 945 2,379,115 Thayer June 26, 1945 2,423,031 Kurtz June 24, 1947 

